Material’s Internal Order Reliably Switches Magnetism Via Linked Atomic Distortions
Summarize this article with:
Antiferroaxial magnetism represents a significant and increasingly recognised ferroic order within condensed matter physics. Yichen Liu and Cheng-Cheng Liu, both from the Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China, demonstrate antiferroaxial altermagnetism as a widespread and fundamentally sound multiferroic mechanism. Their research establishes that antiferroaxial distortions not only induce altermagnetism but also allow for its predictable and reversible control. By employing a unified Landau-theory and symmetry framework, the authors identify a key coupling between antiferroaxial order, the Néel vector, and altermagnetism, deriving general criteria for its existence. This discovery elevates antiferroaxiality as a versatile tool for designing programmable altermagnetic materials with potential applications in spintronics.
Scientists have uncovered a new pathway to control altermagnetism, an unusual magnetic state combining properties of ferromagnets and antiferromagnets, through the manipulation of antiferroaxial order.
This research establishes antiferroaxial altermagnetism as a common and fundamentally sound multiferroic mechanism, where counter-rotating structural distortions not only generate altermagnetism but also allow for its predictable and reversible switching. The work demonstrates a direct link between the antiferroaxial order, the direction of the Néel vector, and the resulting altermagnetic spin splitting, a key characteristic defining this material behaviour. This coupling allows for the reversal of spin splitting simply by reversing the antiferroaxial order, opening possibilities for novel spintronic devices. Researchers developed a unified theoretical framework, combining Landau theory and symmetry analysis, to pinpoint a specific trilinear interaction responsible for this phenomenon. This interaction effectively ‘locks’ the altermagnetism to the antiferroaxial order, ensuring a deterministic response to structural changes. A practical ‘spin group dictionary’ was created, mapping Néel vector configurations to the resulting d-, g-, and i-wave antiferroaxial altermagnetism, providing a guide for predicting and controlling spin splitting. Validation through both ligand-rotation tight-binding models and first-principles calculations confirms the robustness of this mechanism. Furthermore, the study extends beyond theory, identifying numerous candidate materials for antiferroaxial altermagnetism through screening extensive materials databases, MAGNDATA and C2DB. The findings elevate antiferroaxiality to a versatile ‘control knob’ for designing structurally programmable altermagnetic spintronics, potentially leading to new devices with enhanced functionality and energy efficiency. By demonstrating that reversing the antiferroaxial order also inverts time-reversal-odd responses like anomalous Hall conductivity, this work establishes a novel route for structurally controlling spin-based electronics. The study identifies a symmetry-allowed trilinear invariant coupling the antiferroaxial order, the Néel vector, and the altermagnetic order, a critical finding for deterministic and reversible switching of altermagnetism. This coupling locks the induced altermagnetism to the antiferroaxial order, providing a direct link between structural distortion and magnetic behaviour. The practical spin group dictionary maps Néel-vector representations to d-, g-, and i-wave antiferroaxial altermagnetism, offering a guide for predicting spin splitting types. Validation through ligand-rotation tight-binding models and first-principles calculations confirms the mechanism’s broad applicability, extending beyond theoretical prediction to demonstrable physical reality. Screening of the MAGNDATA and C2DB databases identified numerous candidate materials exhibiting this behaviour, suggesting a wide range of potential applications. The work demonstrates that reversing the antiferroaxial order in FeF3 not only switches the spin splitting but also inverts the anomalous Hall conductivity, a time-reversal-odd response. This inversion signifies a novel pathway for structurally programmable spintronics, offering precise control over spin-based devices. This symmetry requirement, Γ1 ⊂ΓG(q) ⊗ΓA ⊗ΓN(q′) ⊗Γl, provides a clear framework for material selection and design. Density functional two-dimensional MnS2 and three-dimensional La2NiO4, to confirm the presence of antiferroaxial altermagnetism. Monolayer MnS2, possessing a parent space group of P 4m2 and constructed from Mn-S4 tetrahedra, underwent detailed analysis. DFT calculations revealed concurrent antiferroaxial and antiferromagnetic instabilities emerging at the M point (q = (π, π, 0)), inducing a rotational distortion of approximately 23.4◦ within the Mn-S tetrahedra. Symmetry analysis identified the order parameters transforming as Gz ∼M2 and N ∼M1, with their combination coupling to the A2 channel of oxygen, as detailed in Supplementary Material Table S1. Subsequent condensation lowered the symmetry to P 421m, indicating g-wave spin splitting, corroborated by the DFT-derived band structure presented in Figure 0.3(c). The three-dimensional Ruddlesden-Popper compound La2NiO4, with a parent space group of I4/mmm and comprising corner-sharing Ni-O6 octahedra, was also examined. Symmetry-mode analysis revealed simultaneous antiferroaxial and antiferromagnetic instabilities at the X point (q = (π, π, 0)), resulting in a rotational distortion of approximately 6.3◦ alongside antiferromagnetic order. The bilinear combination of order parameters transformed as Γ+ 5 (Eg), coupling to the Eg channel of the magnetic multipole oxygen, implying an altermagnetic state. Symmetry reduction occurred to I42/ncm, and further to Pccn, with the Néel order transforming as Γ+ 4 (B3g), corresponding to d-wave altermagnetism, as confirmed by band structure calculations in Figure 0.3(d).
Scientists have long sought robust and easily controlled forms of magnetism for future technologies, but achieving both simultaneously has proven remarkably difficult. This work reframes how we understand the connection between crystal structure and magnetism, specifically through the newly highlighted phenomenon of antiferroaxial altermagnetism. For years, researchers have focused on aligning spins to create magnetism, but this approach often lacks the stability and tunability needed for practical devices. The beauty of this discovery lies in its reliance on the distortion of the crystal lattice itself to induce and control a unique form of spin splitting, offering a pathway to magnetism independent of traditional magnetic ordering. The implications extend beyond fundamental materials science. Altermagnetism, where spins are split but not necessarily aligned, promises energy-efficient spintronic devices, potentially revolutionising data storage and processing. The ability to predictably ‘switch’ this altermagnetic state by manipulating the crystal structure, a ‘ferroic control knob’ as the researchers term it, is particularly compelling. However, the identification of candidate materials through database screening is only a first step. Real-world implementation will demand overcoming challenges in material synthesis and fabrication, ensuring that these predicted properties translate into functional devices. Crucially, the framework presented here isn’t limited to the specific materials investigated. The underlying symmetry principles suggest a much broader range of compounds could exhibit this behaviour, opening up a vast new avenue for materials discovery. Future research will likely focus on exploring these predicted materials, refining the theoretical models, and ultimately, demonstrating the viability of antiferroaxial altermagnetism in prototype devices. The field now shifts from proving the principle to engineering its practical realisation. 👉 More information 🗞 Antiferroaxial altermagnetism 🧠 ArXiv: https://arxiv.org/abs/2602.10641 Tags: